In retailer and exhibition establishments, anti-thief device is used for protecting displayed device from theft. For example, in retailer and exhibition of electronic devices such as mobile phone, digital camera and tablet computer, the exhibited electronic devices are usually electrically connected to a remove-proof device on a display table. When a customer tries to operate and assess the function of an electronic device, the consumer can operate the electronic device directly without disconnecting the electronic device from the remove-proof device; otherwise, the remove-proof device would alarm if the electronic device is disconnected from the remove-proofer device.
The existing anti-theft alarm device is connected to the protected electronic device by an alarm wire. When the alarm wire is disconnected, the anti-theft alarm device would alarm. The alarm wire also provides charging function for the protected electronic device. In general, the alarm wire has a length of about 1.5-2.5 m and an internal resistance about 0.2-1Ω, which may lead to problems such as voltage decay, slow charging or incomplete charging. For example, when a 1 amp (A) current is used for charging a protected electronic device through an alarm wire with a 1-Ω internal resistance, 5 volt (V) voltage outputted from a recharger may decay to 4 V when supplied to the charging terminal of the electronic device, leading to the problems of slow charging or even incomplete charging.